Isolation of specific chemical compounds may be accomplished through different separation techniques based on a variety of properties of materials. Among the most commonly used properties are those involving solubility, volatility, adsorption, and electrical and magnetic effects. A common separation method is column chromatography, whereby individual compounds which were originally present in a mixture are resolved from each other by the selective process of distribution between two immiscible phases, such as liquid and solid.
In one form of column chromatography, called permeation chromatography, molecules from a sample are caused to interact physically with the surface of a porous solid by means of adsorption. The adsorptive effect of the chromatographic medium for different solutes determines their rates of migration through the porous medium which is packed in a tube or column. The sample being processed may either flow through the medium under the influence of gravity or under pressure.
To ensure accurate test results, it is generally desirable that the material comprising the column, as well as any fittings in contact with the sample be non-reactive. This is especially important when separating or purifying polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/PCDF) from environmental and biological samples.
Prior art techniques for processing samples containing dioxins make use of glass, gravity fed chromatography columns. Attempts have been made to make the columns of plastic, such as polypropylene, but this approach has several drawbacks. Ordinary plastic leaches solvents, thus isolation and identification by chromatographic means of extremely small quantities of dioxin may be compromised. However, plastic is much cheaper than its non-reactive alternative: glass. Glass columns are expensive and difficult to ship and work with due to their fragility.